Dyakova Veronika, Kozlov Victor, Polezhaev Denis
Laboratory of Vibrational Hydromechanics, Perm State Humanitarian Pedagogical University and Perm National Research Polytechnic University, Perm, Russia.
Laboratory of Vibrational Hydromechanics, Perm State Humanitarian Pedagogical University, Perm, Russia.
Phys Rev E. 2016 Dec;94(6-1):063109. doi: 10.1103/PhysRevE.94.063109. Epub 2016 Dec 19.
The dynamics of granular medium in a liquid-filled horizontal cylinder with a time-varying rotation rate is experimentally studied. When the cylinder is purely rotated, the granular medium develops an annular layer near the cylindrical wall. The interface between fluid and sand is smooth and axisymmetric. The time variation of the rotation rate initiates the azimuthal oscillation of the liquid in the cylinder's frame of reference and provokes the onset of quasisteady relief in the form of regular dunes. The stability of the axisymmetric sand surface and dynamics of regular dunes are examined. It is found that the ripple formation is provoked by the quasisteady instability of the Stokes boundary layer. In the range of high Reynolds numbers, the ripple formation occurs at a constant critical Shields number θ_{c}≃0.05. The spatial period of the relief is not sensitive to the fluid viscosity and granule diameter; it is determined by the amplitude of oscillation and ratio between the oscillation frequency and mean rotation rate. Long-term experiments show that there are forward and backward azimuthal drifts of dunes. An initial analysis of the issues related to the dune migration is provided.
对充满液体的水平圆柱中随时间变化的旋转速率下颗粒介质的动力学进行了实验研究。当圆柱仅作旋转时，颗粒介质在圆柱壁附近形成一个环形层。流体与沙子之间的界面是光滑且轴对称的。旋转速率的时间变化在圆柱的参考系中引发了液体的方位角振荡，并以规则沙丘的形式引发了准稳态起伏的出现。研究了轴对称砂面的稳定性和规则沙丘的动力学。发现波纹的形成是由斯托克斯边界层的准稳态不稳定性引起的。在高雷诺数范围内，波纹的形成发生在恒定的临界希尔兹数θc≃0.05时。起伏的空间周期对流体粘度和颗粒直径不敏感；它由振荡幅度以及振荡频率与平均旋转速率之比决定。长期实验表明，沙丘存在向前和向后的方位角漂移。对与沙丘迁移相关的问题进行了初步分析。
